Obesity is also a significant public health concern. Although obesity and COC dependence are typically considered distinct clinical entities, both diseases involve perturbations of central biogenic amine and/or hypothalamic-melanocortin systems. The obesity epidemic has spurred development of medications to promote weight loss. A combination of bupropion (BUP) and naltrexone (NTX) is effective for obesity. The overarching goal of this application is to demonstrate the initial efficacy, safety, and tolerability of BUP-NTX combinations for COC dependence. A mixed-model experiment will be conducted in which separate cohorts of non-treatment-seeking, COC-dependent participants will be randomized to different maintenance doses of NTX (i.e., NTX is a between-subject factor). Participants (N=12) in each NTX cohort will be maintained concurrently on BUP (i.e., BUP is a within-subject factor). The reinforcing effects of intranasal COC will be determined after participants in each NTX cohort are maintained for 4-7 days on each of the BUP doses (i.e., COC is a within-subject factor). COC (0, 40 and 80 mg) will be tested with multiple dose combinations of BUP (0, 100, 200, 400 mg/day) and NTX (0, 25, 50 mg/day). The proposed study will also identify the optimal dose combination of BUP and NTX that most effectively attenuates the reinforcing effects of COC.